Search

Concrete-filled steel tube-enhanced steel plate-reinforced concrete (CFST-SPRC) shear walls have been proposed for use in super high-rise buildings. This paper presents an experimental study of CFST-SPRC shear walls that aims to evaluate their seismic behavior. Three CFST-SPRC shear wall specimens with varying steel plate thicknesses and concrete strengths were tested under constant axial force and reversed cyclic loading. All of the specimens experienced a progression of failure from web concrete cracking, to local buckling of the steel tube plates, to fracturing of the vertical welds at the corners. One specimen exhibited brittle failure at the end of testing due to the sudden crushing of web concrete. Stable and full hysteretic behavior was developed by the shear wall specimens, indicating a capability for stable energy dissipation. The ultimate drift ratios were around 1.7% for all of the specimens. The flexural and shear deformations of the shear walls, and the base rotation caused by local deformations in the foundation beam, all provided a negligible contribution to the total lateral displacement. The proportions of the flexural displacement, shear displacement and rotational displacement to the total displacement were around 0.6, 0.2 and 0.2, respectively, for all specimens throughout the loading process. Simplified design methods were proposed for evaluating the load-carrying capacities of CFST-SPRC shear walls. The proposed method provided reasonable but conservative estimations for the test shear wall specimens. [ABSTRACT FROM AUTHOR]

Abstract: In order to improve the ductility of the core wall in super high-rise buildings subjected to high axial compressive force and seismic effect, a new detailed concrete filled double-steel-plate (CFDSP) composite wall using high-strength concrete is proposed. This CFDSP composite wall is composed of concrete filled steel tubular columns at the two boundaries and concrete filled double-steel-plate wall body which is divided into several compartments by vertical stiffeners transversely connected by distributed batten plates. In order to intensively investigate the structural mechanism of this new type of CFDSP composite walls, twelve specimens are tested under large axial compressive force and reversed cyclic lateral load. No evident buckling of surface steel plates can be observed due to reasonable width-to-thickness ratios of steel plates and properly arranged batten plates, so that the surface steel plates and infill high-strength concrete can work compatibly in the whole loading process. All the specimens exhibited good energy dissipation ability and deformation capacity with full hysteretic curves and large ultimate drift ratios, thereby indicating that high-strength concrete can be used in seismic-resistant structures when the proposed new detailed walls are adopted. Based on the test results, the stiffness and strength degradations are analyzed, and the deformation characteristics of all the specimens are discussed in detail. Finally, a strength prediction approach based on the section analysis method is presented, and some detailing requirements for routine design practice are recommended. [Copyright &y& Elsevier]

Abstract: The steel plate shear wall system has been used in a number of buildings as an innovative lateral force resistance system. Stiffened steel plate shear walls possess greater stability and energy absorption during dynamic loading, such as during seismic loading, when compared with unstiffened steel plate shear walls. Openings, however, often exist in the steel plate shear walls due to various functional requirements of the structure. These openings may negatively impact the overall capacity of the shear wall, necessitating additional stiffening. Therefore, an experimental research program was instituted to investigate the seismic behavior of stiffened steel plate shear walls, with and without openings. Strength, stiffness, ductility and energy absorption were evaluated based on the results of reversed cyclic loading tests on three specimens. Two of the test walls had openings, while one wall was constructed without any openings. The test program results showed that stiffened steel plate shear walls exhibit satisfactory seismic behavior, and, as expected, the strength and stiffness characteristics of the walls were reduced in walls with openings. In addition to the test program, an analytical study utilizing a beam–shell mixed Finite Element (FE) model of a single-story wall panel with boundary columns is made to determine the critical factors influencing the shear strength reduction of stiffened wall panels with the opening. Furthermore, extensive numerical calculation and parametric analysis are conducted to derive a simplified formula for the determination of the shear strength reduction coefficient. In addition, complex elasto–plastic FE models of the three specimens are developed to investigate in detail the lateral force resistance behavior of stiffened steel plate shear walls. Good agreement is observed between the experimental and numerical results. Finally, a design method for calculating the lateral resistance capacity, based on the test program and the FE model analysis, is recommended to be used for the routine design practice of stiffened steel plate shear walls. [Copyright &y& Elsevier]

The concrete-filled double-skin steel tubular (CFDST) structures show high strength, large stiffness and convenient construction, which has been adopted in engineering practice more and more widely. However, the nonlinear shear behaviour of CFDST is still lack of research when the shear span ratio is low. This study conducts shear tests on four CFDST deep beams with large diameter of 1500 mm as well as low shear span ratio of 0.33 and 0.83, based on the application of CFDST in a typical nuclear engineering. The failure modes, load-displacement relations, concrete cracks and strains on steel tubes are carefully analysed. Then a refined nonlinear finite element model is built and the shear mechanism of the CFDST is revealed. The shear contribution of various components is obtained including the outer and inner steel tubes, the in-filled concrete, the stiffeners. Parametric analysis is further conducted to find the influence of key design parameters including hollow ratio, material strength and thickness of steel plate. Finally, based on test results and finite element analysis, a shear capacity formula considering the superposition of concrete, steel tube and stiffeners is proposed. It is demonstrated that the CFDST beams show typical shear failure for shear span ratio of 0.33 while shear-flexure failure for shear span ratio of 0.83. The shear strength is high with satisfied ductility. The proposed formula gives accurate prediction which is verified by test results and finite element analysis. • Shear tests are conducted on four CFDST deep beams with large diameter and low shear span ratio. • CFDST beams show shear and shear-flexure failure for shear span ratio of 0.33 and 0.83, respectively. • Shear contribution of various components is obtained including steel tubes, in-filled concrete and stiffeners. • Parametric analysis is conducted to find the influence of key design parameters. • A shear capacity formula considering superposition of concrete, steel tube and stiffeners is proposed. [ABSTRACT FROM AUTHOR]

The steel-concrete (SC) or steel-concrete-steel (SCS) composite structures are widely used in large-scale structures like immersed tunnels, protection structures, etc., due to their superior performances in capacity, ductility, waterproofness, construction efficiency, etc. The steel plates in these structures are usually stiffened with ribs to increase the out-of-plane rigidity and to improve the local buckling performance. While there have been several applications, the buckling design of the composite stiffened plates, based on the methods for steel structures, is still immature and conservative. To deal with this problem, a selected series method (SSM) based the energy theory is proposed, which could both be utilized in composite stiffened plates and steel stiffened plates. The special series shape functions, which could efficiently and accurately represent the 3-dimentional spatial buckling deformation of the stiffened plates with multiple stiffeners, are selected. The explicit high-order solutions for the buckling stress of stiffened plates are derived. Furthermore, a finite element model (FEM) is established. Based on the FEM, a numerical database including most common design parameters is derived, and extensive numerical analyses are conducted to modify and verify the proposed SSM. It is found that, for steel structures, the SSM has a 10%–20% improvement in accuracy compared with the existing methods, and for composite structures, the SSM fills the blank in this area and has acceptable accuracy for design. Finally, from the above studies, the design suggestions are given and discussed. • The buckling behaviors of stiffened composite plates used in large-scale structures are studied. • The selected series method is proposed for the design of stiffened composite/steel plates. • The selected series method is modified and validated using finite element results. • The proposed method improves the accuracy compared with existing methods. [ABSTRACT FROM AUTHOR]

• A sophisticated constitutive model is improved to consider the stress states with damage. • The proposed model is more accurate than built-in models in commercial FE packages. • The proposed model can accurately simulate SPSWs with diverse construction configurations. • Both the beneficial and adverse effect of the axial forces are revealed. • Reasonable suggestions for engineering design considering the axial forces are provided. Extensive numerical research on steel plate shear walls (SPSWs) has been conducted for decades to facilitate their engineering applications. However, these studies usually adopted built-in constitutive models in commercial finite element (FE) packages and focused on SPSWs with a particular type of construction configuration, thus yielding unsatisfactory accuracy and inadequate validation. In addition, the effect of axial forces on the frame columns, which commonly exist in practice, has rarely been investigated. In this paper, a sophisticated constitutive model for structural steel is introduced and further improved by incorporating the Bao and Wierzbicki ductile damage criterion to consider strength degradation under large deformations. Then, 12 SPSW specimens with diverse construction configurations are simulated with the developed model to fully validate its effectiveness. Compared with built-in models in commercial FE software, the developed model is more accurate and can describe complicated deformation patterns under various circumstances, including extreme loading cases. On these bases, a thorough parametric analysis of 35 specimens – combining 5 construction configurations with 7 axial force ratios – is performed to quantitatively investigate the effect of axial forces applied on the frame columns. The results indicate that the axial forces can counteract the tensile forces from the tension fields; but meanwhile can also aggravate the compressive burden of the compression-side column, which induces column yielding or buckling. When the axial force ratio increases, the adverse effect gradually prevails over the beneficial effect and notably decreases the loading capacities. Accordingly, a limit axial force ratio of 0.5 and a simple linear reduction factor when calculating the ultimate loading capacity under axial forces are suggested in engineering design. [ABSTRACT FROM AUTHOR]

• A new type of steel-UHPC composite slab (SUCS) is proposed. • Full-scale tests on steel-UHPC composite slabs are conducted. • Calculation method of bending capacity for composite slabs is developed. • The formulas for predicting flexural stiffness of SUCS are presented. Steel-concrete composite slabs are often used as bridge decks and floors in buildings. This study examines the mechanics of composite slabs that are composed of steel plates and UHPC. Full-scale experiments of three steel-UHPC composite slabs and one steel–concrete composite slab are carried out to investigate how the number and type of shear connectors can affect mechanical behavior. Experimental results showed steel-UHPC composite slabs experienced flexural failure while steel–concrete composite slab experienced punching failure. Experimental data also demonstrated that steel-UHPC composite slabs possess superior ductility, capacity and stiffness. Among the composite slabs, the specimen with sufficient perfobond rib shear connectors (i.e. PBL shear connectors) exhibited the best flexural performance. Subsequently, the experimental results are used to develop a method to predict the bending capacity for composite slabs while taking the tensile contribution of the UHPC and the location of the cross-sectional neutral axis into consideration. The method is applicable to the specimens in this study as well as other specimens described in literature. The proposed formulas for calculating the flexural stiffness of composite slabs can accurately reproduce the load–deflection behavior for specimens under service loads. Results from this paper can guide engineers in the practical application of steel-UHPC composite slabs. [ABSTRACT FROM AUTHOR]

• Four innovative flexural critical composite shear walls without tie bars were proposed and tested. • The failure mode, load-displacement relationship and stiffness degradation behavior were investigated. • The proposed systems connected by shear studs exhibited adequate strength and displacement capacity. • The shear force contribution of steel plate was obtained and overstrength ratio was proposed. The reinforced concrete filled composite plate shear walls (CPSW) system employs two steel plates with infilled reinforced concrete. Based on an experimental study of four flexural critical CPSW specimens under high axial compression ratio ranging from 0.313 to 0.542 and reciprocal lateral load, the seismic performance of shear studs connected CPSW systems with orthogonal reinforcement in wall web and longitudinal reinforcement in boundary element is examined. The failure mode, load-displacement relationship, flexural strength, displacement capacity, stiffness degradation and equivalent damping ratio are reported in detail. The compression yielding of boundary element was observed before its local buckling, and yielding of faceplate was observed before faceplate local buckling. The fracture failure of the boundary element and crushing of infilled concrete were observed at the descending branch. The test results showed that the CPSW systems connected by shear studs had adequate ductility, and the ultimate drift ratio ranged from 1.17% to 1.78%. The overstrength ratio of the moment capacity ranged from 1.06 to 1.18 in the test. Based on the plasticity theory, the strain measurement results of steel faceplates were used to calculate the shear force contribution of the steel plate. The influence of axial compression ratio on the internal force transfer and ultimate capacity is investigated. In addition, a database of 47 flexural critical CPSW specimens with boundary element was established, and the overstrength ratio for the anchorage design was proposed with adequate safety. [ABSTRACT FROM AUTHOR]